Final answer:
The popular Christmas song described in the question is most likely 'Loveliest of Trees' by John Rutter.
Step-by-step explanation:
The Christmas song described in the question is most likely 'Loveliest of Trees' by John Rutter. Although it is not a rock song, it is a popular Christmas carol with a sentimental feel. The lyrics mention a tree covered in bloom, which suggests it is a cherry tree during the spring season.